Most people (90%) are right-handed and have dominant motor control in their left hemisphere. There are some intriguing differences between right- and left-handed populations.

No one knows, however, why left-handedness develops. As with most other human traits, theories can be roughly divided into four categories: environmental, genetic, developmental, and evolutionary.

For example, males are more likely to be left-handed than females.

1. Identify at least one other difference between right and left-handed populations.

2. Explain how just one of these theories tries to justify differences between right and left-handed popula